Are post-fire residual forest patches refugia for boreal bryophyte species? Implications for ecosystem based management and conservation

Residual patches of forest remaining after natural or anthropogenic disturbance may facilitate regeneration of fragmented forest. However, residual patch function remains unclear, especially after natural wildfire. We investigate the role of residual boreal forest patches as refugia for bryophytes and ask the question, do they house bryophyte communities similar to those encountered in undisturbed forests? Bryophytes were sampled in three habitat types in black spruce boreal forests illustrating a gradient of disturbance severity: undisturbed forests, residual patches and burned matrices. Temporal, disturbance severity, spatial and structural variables of habitats were also recorded. Bryophyte community composition differed among habitat types with residual patches characterized by higher species richness, the loss of forest specialists and the addition of disturbance-prone species. The bryophyte community found in residual patches is at the interface between the communities of undisturbed forests and burned matrices. As residual patches did not conserve all species, particularly forest specialists, they were not refugia. However, we identify temporal, spatial and structural characteristics that can maintain bryophyte communities most similar to undisturbed forests and enhance residual patch “refugia potential”. Residual patches enhance bryophyte diversity of the landscape housing species that cannot survive in the burned matrix. As conclusion we discuss the use of retention patches in harvested stands, together with the preservation of undisturbed stands that house singular bryophyte communities and especially sensitive forest specialists.     

Does environmental management improve enterprise's value? – An empirical research based on Chinese listed companies

The company's environmental management behaviors can improve the relationship between the company stakeholders, help companies to sustainably develop. But it is more seen as an obligation and cost of the company's environmental protection in developing countries. So what kind of impact the environmental protection have on the value of the company? Taking Chinese listing Corporation as a sample. This paper analyzes the impact of enterprises’ environmental management and its disclosure on corporate value. We conclude that environmental management excluding independent environment report can improve corporate value. In specific environmental management measures, producing environmental friendly products can help environmental friendly products gain recognition and improve corporate value significantly.     

A predictor of transmembrane α-helix domains of proteins based on neural networks

Back-propagation, feed-forward neural networks are used to predict a-helical transmembrane segments of proteins. The networks are trained on the few membrane proteins whose transmembrane -helix domains are known to atomic or nearly atomic resolution. When testing is performed with a jackknife procedure on the proteins of the training set, the fraction of total correct assignments is as high as 0.87, with an average length for the transmembrane segments of 20 residues. The method correctly fails to predict any transmembrane domain for porin, whose transmembrane segments are -sheets. When tested on globular proteins, lower and upper limits of 1.6 and 3.5% for a total of 26826 residues are determined for the mispredicted cases, indicating that the predictor is highly specific for -helical domains of membrane proteins. The predictor is also tested on 37 membrane proteins whose transmembrane topology is partially known. The overall accuracy is 0.90, two percentage points higher than that obtained with statistical methods. The reliability of the prediction is 100% for 60% of the total 18242 predicted residues of membrane proteins. Our results show that the local directional information automatically extracted by the neural networks during the training phase plays a key role in determining the accuracy of the prediction. Correspondence to: R. Casadio     

Farming for pests? Local and landscape-scale effects of grassland management on rabbit densities

In recent decades in the UK, there has been an increasing trend in numbers of the European wild rabbit, a significant agricultural pest typically associated with grassland habitats. However, the relationship between rabbit abundance and grassland management, in particular grazing, has not been sufficiently explained. We studied rabbit densities in seven pasture-dominated sites in north-east England between autumn and spring in two consecutive years, and used generalised linear mixed models and generalised additive models to explore relationships between habitat and management variables and rabbit abundance at local (field) and landscape scales. At the local scale high rabbit densities were significantly associated with small fields and the very short, homogeneous swards created by intensive sheep grazing during autumn and winter. At the landscape scale, high rabbit numbers were associated with sites with most field margins and a predator removal policy. Our results indicate that landscape management may play a central role in explaining rabbit abundance and distribution in grasslands. We suggest that current pasture management may create favourable conditions for high rabbit densities, and consequently boost numbers of this significant pest species.     

How good are Bayesian belief networks for environmental management? A test with data from an agricultural river catchment

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Is there a unifying mechanism for protein folding?

Proteins appear to fold by diverse pathways, but variations of a simple mechanism - nucleation-condensation - describe the overall features of folding of most domains. In general, secondary structure is inherently unstable and its stability is enhanced by tertiary interactions. Consequently, an extensive interplay of secondary and tertiary interactions determines the transition-state for folding, which is structurally similar to the native state, being formed in a general collapse (condensation) around a diffuse nucleus. As the propensity for stable secondary structure increases, folding becomes more hierarchical and eventually follows a framework mechanism where the transition state is assembled from pre-formed secondary structural elements.     

Evolutionary deimmunization: an ancillary mechanism for self-tolerance?

Self-proteins in the extracellular environment are constantly sampled and processed through the Class II antigen presentation pathway. Mechanisms responsible for central and peripheral tolerance reduce the chance of autoimmune responses to these proteins. However, tolerance can and does break down, leading to the development of autoimmune disease. In a preliminary analysis, we observed that common serum proteins have fewer HLA class II-restricted T-cell epitopes than expected, when compared to random protein sequences. We therefore performed a broader analysis of human proteins to determine whether the number of T-cell epitopes in extracellular proteins is reduced in comparison with non-secreted (intracellular) proteins. Here we document fewer putative HLA class II-restricted T-cell epitopes in extracellular proteins, compared to intracellular proteins. These data suggest that the diminished presence of T-cell epitopes may reduce the potential for autoimmunity. Over evolutionary timescales, immune pressure may have resulted in alterations in the inherent T-cell immunogenic potential of autologous proteins.     

Synchrony: a neuronal mechanism for attentional selection?

Attentional selection involves brain processes that select and control the flow of information into the mechanisms that underlie perception and consciousness. One theory proposes that the neural activity that represents the stimuli or events to be attended to is selected through modification of its synchrony. Recent experimental evidence supports this theory, by showing that changes in attentional focus increase the synchrony of neural firing in some neuron pairs and decrease it in others.     

Microparticles, stem cells'new mechanism for tissue repair?

Though stem cell transplantation has been confirmed to be useful in repairing aging and diseased tissues, the underlying mechanism remains elusive. In addition to soluble molecules, cells-derived membrane microparticles (MPs) are considered as new mediators served in cross-talk communication among cells. MPs are tiny membrane coated subcellular vesicles released by a variety of cell types including stem cells. MPs may interact with target cells through specific receptor-ligand interactions and transfering proteins, bioactive lipids, mRNA and miRNA. Composition and function of stem cells derived MPs are highlighted in recent years. Here, we give an overview of MPs'composition, vesiculation and liberation mechanism, roles involved in communication exchages, and research progress in stem cells derived MPs. The report here might provide some novel information to highlight the stem cells therapy.     

Does superoxide channel between the copper centers in peptidylglycine monooxygenase? A new mechanism based on carbon monoxide reactivity

Peptidylglycine monooxygenase (PHM) carries out the hydroxylation of the alpha-C atom of glycine-extended propeptides, the first step in the amidation of peptide hormones by the bifunctional enzyme peptidyl-alpha-amidating monooxygenase (PAM). Since PHM is a copper-containing monooxygenase, a study of the interaction between the reduced enzyme and carbon monoxide has been carried out as a probe of the interaction of the Cu(I) sites with O(2). The results show that, in the absence of peptide substrate, reduced PHM binds CO with a stoichiometry of 0.5 CO/Cu(I), indicating that only one of the two copper centers, Cu(B), forms a Cu(I)-carbonyl. FTIR spectroscopy shows a single band in the 2200-1950 cm(-)(1) energy region with nu(CO) = 2093 cm(-)(1) assigned to the intraligand C-O stretch via isotopic labeling with (13)CO. A His242Ala mutant of PHM, which deletes the Cu(B) site by replacing one of its histidine ligands, completely eliminates CO binding. EXAFS spectroscopy is consistent with binding of a single CO ligand with a Cu-C distance of 1.82 +/- 0.03 A. The Cu-S(met) distance increases from 2.23 +/- 0. 02 A in the reduced unliganded enzyme to 2.33 +/- 0.01 A in the carbonylated enzyme, suggesting that the methionine-containing Cu(B) center is the site of CO binding. The binding of the peptide substrate N-Ac-tyr-val-gly perturbs the CO ligand environment, eliciting an IR band at 2062 cm(-)(1) in addition to the 2093 cm(-)(1) band. (13)CO isotopic substitution assigns both frequencies as C-O stretching bands. The CO:Cu binding stoichiometry and peptide/CO FTIR titrations indicate that the 2062 cm(-)(1) band is due to binding of CO at a second site, most likely at the Cu(A) center. This suggests that peptide binding may activate the Cu(A) center toward O(2) binding and reduction to superoxide. As a result of these findings, a new mechanism is proposed involving channeling of superoxide across the 11 A distance between the two copper centers.     

Density-dependent switches in diet: a likely mechanism for negative feedbacks on goose population increase?

Goose grazing on arctic tundra vegetation has shown both positive and negative effects on subsequent foraging conditions. To understand the potential of a density-dependent feedback on herbivore population size, the relation between grazing pressure and future foraging conditions is essential. We studied the effect of increasing grazing pressure of barnacle geese (Branta leucopsis) on Spitsbergen. During the establishment of a breeding colony in the period 1992–2004, the proportion of graminoids decreased in the diet of wild geese, while the percentage of mosses increased. Grazing trials with captive geese in an unexploited area showed a similar shift in diet composition. High-quality food plants were depleted within years and over years. Intake rate declined too and as consequence, metabolisable energy intake rate (MEIR) decreased rapidly with increasing grazing pressure. During three successive years of experimental grazing, MEIR decreased at all levels of grazing pressure and declined below minimal energetic requirements when grazing exceeded natural levels of grazing pressure. This suggests that foraging conditions rapidly decline with increasing grazing pressure in these low-productive habitats. The potential for density-dependent feedbacks on local population increase is discussed.     

Localization algorithm in wireless sensor networks based on semi-supervised manifold learning and its application

Localization of mobile nodes in wireless sensor network gets more and more important, because many applications need to locate the source of incoming measurements as precise as possible. Many previous approaches to the location-estimation problem need know the theories and experiential signal propagation model and collect a large number of labeled samples. So, these approaches are coarse localization because of the inaccurate model, and to obtain such data requires great effort. In this paper, a semi-supervised manifold learning is used to estimate the locations of mobile nodes in a wireless sensor network. The algorithm is used to compute a subspace mapping function between the signal space and the physical space by using a small amount of labeled data and a large amount of unlabeled data. This mapping function can be used online to determine the location of mobile nodes in a sensor network based on the signals received. We use independent development nodes to setup the network in metallurgical industry environment, outdoor and indoor. Experimental results show that we can achieve a higher accuracy with much less calibration effort as compared with RADAR localization systems.     

Should artificial neural networks replace linear models in tree ring based climate reconstructions?

Studies focused on tree ring—climate relationships usually use linear methods to find the optimal transfer function. In our study, three sites with three different tree species from the Western Balkan region were selected to compare linear and artificial neural network (ANN) nonlinear models and to see whether linear models can be potentially replaced with ANN in climate reconstruction. For each site, one linear and two different ANN models were calculated. For all analysed sites, we were able to find a better fit using the advanced technique of ANN. All calibration and verification statistics were in favour of ANN models. A climate variable was reconstructed for a selected site using linear and nonlinear ANN methods. We demonstrated that ANN is always a more effective method, which always produce better results than linear models. The key to success is a properly selected training algorithm, which prevents overfitting and is able to find the optimal transfer function, also linear, if that is the case.     

Double-liposome - based dual-drug delivery system as vectors for effective management of peptic ulcer

The aim of the present investigation was to prepare and evaluate a vesicular dual-drug delivery system for effective management of the mucosal ulcer. Inner encapsulating and double liposomes were prepared by the glass-bead and reverse-phase evaporation methods, respectively. The formulation consisted of inner liposomes bearing ranitidine bismuth citrate (RBC) and outer liposomes encapsulating amoxicillin trihydrate (AMOX). The optimized inner liposomes and double liposomes were extensively characterized for vesicle size, morphology, zeta potential, vesicles count, entrapment efficiency, and in vitro drug release. In vitro, the double liposomes demonstrated a sustained release of AMOX and RBC of 93.6 ± 1.9 and 84.1 ± 0.9%, respectively, at the end of 144 hours. Ex vivo studies were conducted on Helicobacter pylori (ATCC26695) bacterial cell lines. Double liposomes showed a more enhanced percent H. pylori growth inhibition than the plain drug combination. Further, in vivo studies illustrated enhanced antisecretory and ulcer-protective activity of double liposomes, as compared to the plain drug combination. Microscopic studies also supported the ulcer-protective action of the formulation. Thus, it may be concluded that double liposomes are instrumental in reducing gastric secretions and targeting ulcer sites with the interception of minimal side effects, thus suggesting their potential in ulcer therapy.     

Nuclear assembly of UGA decoding complexes on selenoprotein mRNAs: a mechanism for eluding nonsense-mediated decay?

Recoding of UGA from a stop codon to selenocysteine poses a dilemma for the protein translation machinery. In eukaryotes, two factors that are crucial to this recoding process are the mRNA binding protein of the Sec insertion sequence, SBP2, and the specialized elongation factor, EFsec. We sought to determine the subcellular localization of these selenoprotein synthesis factors in mammalian cells and thus gain insight into how selenoprotein mRNAs might circumvent nonsense-mediated decay. Intriguingly, both EFsec and SBP2 localization differed depending on the cell line but significant colocalization of the two proteins was observed in cells where SBP2 levels were detectable. We identify functional nuclear localization and export signals in both proteins, demonstrate that SBP2 undergoes nucleocytoplasmic shuttling, and provide evidence that SBP2 levels and localization may influence EFsec localization. Our results suggest a mechanism for the nuclear assembly of the selenocysteine incorporation machinery that could allow selenoprotein mRNAs to circumvent nonsense-mediated decay, thus providing new insights into the mechanism of selenoprotein translation.